Here is an easy way to write in Japanese. but it might be only for XP.

1. Go to the control panel.
2. Go to Language and Regional Optiopns (you might need to switch
to classic view).
3. Go to the Languages tab.
4. If the Install Files for East Asian Languages box isn't checked,
check it and click OK.
5. Click on Details...
6. Click on Add...
7. Select Japanese from the list and click OK. A little thingie in the
bottom right of your toolbar will show up, this is the Language Bar.
It will proably say EN.
8. Whenever you want to type in Japanese, click on it and select JP.
9. Right click and select Restore the Language Bar.
10. Click on the A and choose hiragana. The A should change to あ.
11. Now you will write in Japanese.
12. If you want to change back, click the あ and select Driect Input.
13. Anything else is pretty easy to figure out.